The ability to maintain spatial orientation and balance is the result of an elaborate synchronization of neural inputs from the vestibular, visual, and proprioceptive systems. When there is a mismatch among these signals or when input patterns from different senses do not correspond to stored expected sensory patterns, spatial disorientation may occur. The two primary conflicts occur between the visual and vestibular senses (i.e., intersensory conflict) and within the vestibular sense between the semicircular canals and otoliths (i.e., intrasensory conflict). Secondary conflict, however, may come from proprioceptive inputs that fail to synchronize with other sensory cues, particularly visual and peripheral proprioceptors connected to the vestibular system through vestibulospinal pathways. This creates the sensation commonly known as Motion Sickness. It includes a range of symptoms, from nausea and salivation to a sensation of warmth, tiredness, and other cognitive symptoms. In addition, sensory conflicts remain one of the most persistent issues facing advanced flight simulation development. Flight simulators have been shown to improve training effectiveness with considerably lower cost and risk than actual flight training. The capability to use simulation in training brings advantages in acquisition of skill sets, development of competencies, the reduction of errors in real environments, and decreased costs. The simulation environment, however, imposes limitations in matching real world sensory experiences. These limitations may manifest in the form of simulator-induced motion sickness, also known as simulator sickness (SS). SS is a variant of motion sickness resulting from exposure to simulated environments such as flight simulators, driving simulators and similar virtual, immersive environments. Whereas motion sickness refers to the adverse consequences of exposure to environments that physically put an individual in motion, SS is mainly the result of technological limitations in simulating dynamic environments that create a conflict in the body's self-motion perception sensors. Because of the wide variety of these symptoms, such as nausea, oculomotor disorders, disorientation, and the like, SS has also been described as “polygenic” since several factors have been identified including age, gender, simulator features, e.g., lag and field of view (FOV), and factors associated with the task performed, e.g., duration and degree of control. The theory of sensory conflict, also known as the sensory rearrangement or neural mismatch theory, indicates that sickness occurs when the pattern of inputs from different senses and within a single sensory modality do not correspond to the stored patterns of such inputs based on past experience, as a result of both cognitive and perceptual discrepancy. When SS symptoms develop, the value of the training experience and data derived during the experience may be compromised and in the most extreme cases results in negative transfer-of-training. Moreover, since symptoms may persist or recur spontaneously up to one day after exposure, various training centers routinely ground pilots for 6 to 24 hours after simulator time. These factors can lower the acceptance and overall utility of simulator enhanced learning. Conventional preventative pharmacological agents commonly used for motion sickness are typically ineffective to prevent SS and may be commonly associated with significant side effects after the simulated sessions including drowsiness and fatigue. Thus, simulator design may have a significant role in decreasing the incidence of SS. However, even with technological advances, imperfections including optical deficiencies, image scale factor magnifications, system time delays, limited field of view (FOV) displays head tracker inaccuracies, and the like, still remain unsolved limitations which contribute to SS.
Thus there is a need to mitigate motion sickness and/or SS by reducing or eliminating the mismatch between sensory cues inputs expected by a human subject and improve simulation based training.